Various methods for producing carbon nanotubes and nanowires are known and the various applications are proposed. Production of non-carbon nanotubes and nanowires are being attempted.
For example, “Applied Physics Letters Volume 79 Number 10, 3 Sep. 2001” (pages 1546-1548) discloses a method for growing silicon nanowires from a silicon alloy ball. This method makes hydrogen radical react with silicon hydrogen compounds (SiHx) in presence of Ga as a catalyst, takes xH out of SiHx to produce a Ga—Si alloy and grows silicon wires from the alloy. This reaction is expressed by the following equation.
                                          SiH            x                    ⁢                                          ⁢                      (            g            )                          +                              x            ⁢            H                    ⁢                                          ⁢                                    (              g              )                        ⁢                                                  ⁢                          ⟶              Ga                        ⁢                                                  ⁢            Ga                          -                  Si          ⁢                                          ⁢                      (            l            )                          +                                            x              ⁢              H                        x                    ⁢                                          ⁢                      (            g            )                                              (        1        )            
The diameter of the produced silicon nanowire dx is expressed by the following equation.
                              d          x                =                              4            ⁢            Ωα                                RT            ×                          ln              (                              C                                  C                  x                                            )                                                          (        2        )            where,    R: gas constant    T: temperature    Ω: molar volume    α: surface free energy    C: silicon concentration in an alloy    Cx: equilibrium concentration
Japanese laid-open patent application No. 2000-48929 discloses a method for growing a silicon nanotube from an alloy ball by separating silicon out from a droplet (melt state) alloy of Au and silicon.
In this production method, a SiO2 film 92 is formed on the surface of a silicon substrate 91 as shown in FIG. 14(A), and a circular aperture 93 is formed on the SiO2 film 92 by etching as shown in FIG. 14(B). Au is deposited in the circular aperture 93 to 2-10 nm thickness by sputtering. Au particles are generated in each circular aperture 93 by heating the silicon substrate 91 to 650-800° C.
The Au particle melts and becomes a droplet 94 of Au—Si alloy ball by reacting with the silicon substrate 91 as shown in FIG. 14(C). A silicon contained compound gas, e.g. SiH4, SiHCl3, SiH2Cl2, Si2H6 is integrated into the Au—Si alloy ball (droplet 94).
The patent document 1 teaches that the silicon in the Au—Si alloy ball (droplet 94) separates out and a silicon nanotube 95 grows from the round of the droplet as shown in FIG. 14(D). In the patent document 1, the silicon nanotube 95 is “fullerene” and the silicon nanotube in this document is considered “silicon nanowire” in actual.